Hello all, I need some advice. I have been trying to reset the check engine light and up shift arrow light on my Volvo 850.

Below is a shortened list of what I have done so far. Any advice would be considered useful, I am at the point where I want to douse it with gasoline, light a match and walk away.

The codes that I started with are as follows.

A-1 Transmission fault codes

124 (mode selector switch, installed a used one, no change)
114 (PNP, cleaned, then tried a different one, no chnage)
222 (transmisison S2 solenoid) Installed a new S2 solenoid, all old codes cleared but immediately got a new code, 122 which is for the S1 solenoid

It seems a little to coincidental that the code immediately came on as soon as I finished replacing the S2 transmission solenoid

I know that it is recommended that I replace all three at once, but come on, I am a little frustrated by the result of replacing the S2. Is there anything else I should check? The transmission control computer? Ir should I


A-2 Engine fault codes

2-1-3 TPS Fault at full load -caused by air intake hose? (Replaced air intake hose)

2-1-4 RPM signal reversed or faulty - dirty RPM signal? Cleaned sensor, seems ok now

so, lots of codes, what do you think, change the S1 solenoid, replace the transmission, which was somewhat dirty inside, or look at some other cause such as the transmission computer?

please help.
thanks
alek